Pusher type centrifuge with a washing device for the centrifuged material



Nov. 5, 1968 F. w. SCHNEIDER v 3,409,137

PUSHER TYPE CENTRIFUGE WITH A WASHING DEVICE FOR THE CENTRIFUGEDMATERIAL Original Filed Aug. 24, 19 1 2 Sheets-Sheet 1 Nov.'5, 1968 F.w. SCHNEIDER 3,409,137

PUSHER TYPE CENTRIFUGE WITH A WASHING DEVICE FOR THE CENTRIFUGEDMATERIAL Original Filed Aug. 24, 1961 2 Sheets-Sheet 2 In 14 .555; 20 M2 22 A A I I4a H 14b v I jm emorz' IF Wm United States Patent 2 Claims.of. 210-213 ABSTRACT OF THE DISCLOSURE A pusher type centrifuge with awashing device for the centrifuged material, which comprises a housingand a centrifugal drum rotatably mounted in the housing to constitute afirst member. Two cylindrical screen portions, having differentdiameters, extend axially from the centrifugal drum. A pusher plate isdisposed within the housing and rotates coaxially with, as well asreciprocates relative to the centrifugal drum, the pusher plateconstituting a second member. A conically outwardly wideningsolid-walled portion is secured to one of the members and is disposed ata greater radial range relative to the rotating axis than the outermostradius of the pusher plate, as well as extending from one of thecylindrical screen portions to the other of the cylindrical screenportions. An inwardly widening acceleration funnel is secured to one ofthe members for joint rotation therewith. A feeding pipe leads into theacceleration funnel and a washing pipe is arranged for feeding washingliquid toward the solid-walled portion.

This is a continuation application to my co-pending patent applicationSer. No. 133,664, filed on Aug. 24, 1961, and now abandoned.

The present invention relates to a pusher-type centrifuge with a washingdevice for the centrifuged material.

Single-stage, as well as multi-stage pusher-type centrifuges are knownfor the continuous separation of liquidsolids mixtures.

In a single-stage pusher-type centrifuge a pusher plate reciprocatesaxially along a portion of the inner wall of the centrifugal drum duringthe rotation of the cylindrical or conical centrifugal drum which iscovered with screens and, thereby, the filter cake, which is depositedon the inner wall, is gradually conveyed to the discharge end of thecentrifugal drum, where it is thrown out into the collecting chamber forthe solids.

In a multi-stage pusher-type centrifuge several cylindrical or conicalfilter-drum parts are fitted telescopically one inside the other andconnected to two systems, reciprocating axially relative to each otherin such manner, that any two immediately adjacent drum parts belong todifferent systems. The end faces of all inner drum parts operate thenalways as pusher members for the discharge of the filter cake which isdeposited on the inner wall of the outwardly adjoining adjacent outerdrum part.

It has been found, that in the centrifuging of hard granular orcrystalline materials, single-stage pusher-type centrifuges with acylindrical filter are superior to multistage pusher-type centrifugeswith cylindrical filters and are also superior to the pusher typecentrifuges with tapered filters in that they provide a low residualmoisture and a high yield of solids. This advantage is explained by thefact that in single-stage pusher-type centrifuges with a cylindricalfilter part, the filter cake is 3,409,137 Patented Nov. 5, 1968 built uponce only, that is it is not turned over several times and, due to thefact that a bridge formation of its particles takes place, it holds backeven fine materials.

Multi-stage pusher-type centrifuges are used advantageously, when thefilter cake must be washed or when vlscous or thixotropic substances areto be centrifuged. The better effect of the multi-stage pusher-typecentrifuges for these materials resides in the multiple restratificationand loosening of the filter cake during each transfer from one drum tothe next drum of larger diameter. The loosening encourages thepenetration of the washing liqaid and the removal of the originallybonded interstitial liquid or mother liquor. Since the loosening andrestratification are restricted to a relatively small area, a pluralityof washing stages, that is, drum stages, must be arranged in series whenlarger quantities of washing liquid are to be bonded. Thus, pusher-typecentrifuges with a total of eight stages are known, which entail ratherhigh manu facturing costs due to their involved construction. Due to thealways new building up of the filter cake, upon the transfer from onedrum to the next, as well as due to the great number of ring slotsbetween the sliding rings and the screens, a high solids loss in thefiltrate must be ac cepted in the multi-stage pusher-type centrifugeand, thereby, a lower yield of solids.

The heaviest losses of solids are found in multi-stage pusher-typecentrifuges with conical filter drums, because in this structure theloss of solids occurs not only in the annular gaps between the thrustrings and the drums, but also to a great extent on the conical filterpart itself, because of the continuous loosening of the cake. Thecentrifuging of fine material is possible only to a limited extent inthese centrifuges even with modest requirements concerning the yield ofsolids.

It is one object of the present invention to provide pusher-typecentrifuges with a washing device for the centrifuged material whichavoid the drawbacks of the multi-stage pusher-type centrifugesconcerning the washingpossibilities, the filtrate loss and theconstruction thereof.

It is another object of the present invention to provide pusher-typecentrifuges with a washing device for the centrifuged material with arotating shell of a centrifugal drum and a cylindrical screen part,followed in the discharge direction by a conically widening solid-walledpart, secured to a pusher plate, or the cylindrical screen part securedto the pusher plate to which solid-walled part the washing liquid isfed, and a suitably wider cylindrical filter part which follows thecomically diverging walled part.

The formation of the washing zone as a conical solidwalled part causes aloosening of the filter cake and, thereby, an improved washingpossibility without additional filtrate loss. This solid-walled part canbe rigidly connected with the two adjacent cylindrical screen parts ormay be made axially displaceable relative to one or both of these parts,whereupon a one-, twoor at the most three-stage pusher-type centrifuge,thus a comparatively simple construction, results.

With these and other objects in view which will become apparent in thefollowing detailed description, the present invention will be clearlyunderstood in connection with the accompanying drawings, in whichmultistage pusher-type centrifuges are disclosed:

FIGURE 1 is an axial section of a pusher-type centrifuge, in accordancewith the present invention, and illustrated as a three-stage pusher-typecentrifuge;

FIG. 2 is an axial section of a three-stage pushertype centrifuge anddiscloses another embodiment compared with that of FIG. 1; and

FIG. 3 is an axial section of a two-stage pusher-type centrifuge. V

Multistage pusher-type centrifuges are disclosed, serving to separateliquids from materials which start to flow under the influence of thewashing liquid, for instance which have a fine grain amorphouscharacteristic. Such materials are unable to transmit the axial thrustrequired for the discharge of the material within the range of thewashing zone.

Referring now in particular to FIG. I of the drawings, the centrifugecomprises a housing 27' and is divided into an axially immovablecentrifugal drum 1 which consists of two axially immovable cylindricalfilter portions 12 and 13, the filter portion 12 being connected withthe centrifugal drum 1' by means of stays 12a which extend through bores140 of a pusher plate 14. A conical solidwalled portion 15 having anangle of 20 to 40, reciprocates in the axial direction together with thepusher plate 14 connected thereto by stays 15a and simultaneouslyrotates with the pusher plate 14 and stays 15 and with the centrifugaldrum 1'. A hollow drum shaft 1a is rotatably mounted in the housing 27'by means of ball bearings 1b secured to the housing 27. A reciprocatingshaft 14a is mounted for axial reciprocating movement and simultaneousrotation with the hollow drum shaft 1a in the latter by means of slidebearings 14b. The hollow drum shaft 1a is rigidly secured to thecentrifugal drum 1 to rotate jointly with the hollow drum shaft 1a. Thereciprocating shaft 14a is secured to the pusher plate 14, wherebyrotation as well as axial reciprocating movement is conferred to thepusher plate 14, as well as to the conical solid-walled portion 15connected with the pusher plate 14. The solids are taken up in thisembodiment, upon moving to the right stepwise by the axiallyreciprocating pusher plate 14, which is sealed at its periphery bypiston ring-like members 8 consisting of elastic material and therebyreaches the conical solid-walled portion 15 during its axial movementalong the first screen portion 12 of the centrifugal drum 1' and thecomparatively long washing zone along the solid-walled portion 15 of thepusher plate 14, from the end faces of the filter portion 12 operatingas a pusher ring and of the solid-walled portion 15 and moved forwardlyto the collecting chamber 11'. A feeding pipe 5 for the material to becentrifuged enters the housing 27 and terminates in an accelerationfunnel 6, which is connected with the pusher plate 14 by means of stays7' and rotates with the latter together with the centrifugal drum 1. Atthe solid-walled portion 15 of the filter cake is loosened due to thecontinuous increase of the diameter of the portion 15, whereby thepenetration of washing liquid simultaneously fed by means of a pipe 9'and the nozzle 10 is favored. Due to the formation of the conicalportion as a solid wall, neither a passage of solids, nor a filtrateloss occurs in the loosening and washing zone. The washing liquid flowsalong the inner portion of the solid-walled portion 15 into acylindrical screen portion 13 projecting axially from the solid-walledportion 15, in which portion 13 the cake is no longer subjected to anyturn-over movements, which could start or favor the passage of solidsthrough the screen openings. The cake is centrifuged dry from thecylindrical filter portion 13, the centrifuged liquid being caught inthe filtrate collecting chamber and the solids at the right end arefinally thrown out into the collecting chamber 11' for the solids.

Substantially the same effect is brought about in the centrifugedisclosed in FIG. 2 which again comprises a housing 27 In deviation fromthe embodiment disclosed in FIG. 1, however, the conical solid'walledportion 16 is secured by means of radial stays 17 to the accelerationfunnel 18, which in turn is connected to a pusher plate 14 by means ofstays 17. A hollow shaft 1a is in this embodiment again mounted in thehousing 27 by means of ball bearings lb A reciprocating shaft 14a isaxially movable in the hollow shaft 1a by means of slide bear ing 1419and rotatable with the hollow shaft la The reciprocating shaft 1411 issecured to the pusher plate 14 and axially movable with the latter. Thewashing liquid is fed through a pipe 19 into a drum 20 which is alsoconnected with the acceleration funnel 18. The shell of the drum 20 isequipped with spray-nozzles 21, which cause hitting uniformly theopposite face of the washing zone with the washing liquid. In order toavoid an overflow of the drum 20, radial bores 22 are provided in thestays 17 through which bores 22 the washing liquid may run off in caseof feeding too great quantities thereof, or in case of clogging up ofthe nozzles 21. The arrangement providing a rotation of the washingnozzles 21 is of advantage, since it prevents the otherwise unavoidableatomization experienced in immovable nozzles, which atomization canpenetrate into a collecting chamber 11 for the solids. Screen portions12 and 13: are secured to the centrifugal drum 1 as disclosed in FIG. 1.A feeding pipe 5 for the material is provided as in the previousembodiments.

Referring now again to the drawings and in particular to FIG. 3, inwhich a pusher-type centrifuge with two stages is disclosed andcomprises a housing 27 and the centrifugal drum 1 carries a screenportion 25. A pusher plate 14 secured to a reciprocating shaft 14a hassecured thereto another filter portion 24, to which is connecteddirectly a conical solid-walled portion 23, while the first mentionedfilter portion 25, as stated above, is connected with the centrifugaldrum '1 A pusher bottom 26 is connected with the centrifugal drum 1 bymeans of stays which extend through bores 14c of the pusher plate 14 torotate with the centrifugal drum 1 An acceleration funnel 6 is securedby means of stays 27 to the pusher bottom 26. A reciprocating shaft 14ais again secured to the pusher plate 14 and a hollow shaft 1a isprovided in the same manner as disclosed in the previous embodiments bymeans of ball bearings 1b carrying slide bearings 14b for thereciprocating shaft 14a A washing pipe 9 having a nozzle 10 and afeeding pipe 5 are again arranged. In this embodiment the advantage of acomparatively long washing zone is also present.

While I have disclosed several embodiments of the present invention, itis to be understood, that these embodiments are given by example onlyand not in a limiting sense, the scope of the present invention beingdetermined by the objects and the claims.

I claim:

1. In a pusher type centrifuge with a washing device for the centrifugedmaterial:

a housing,

a centrifugal drum rotatably mounted in said housing,

to constitute a first member,

at least one first cylindrical screen portion extending axially fromsaid centrifugal drum,

a pusher-plate disposed within said housing and rotating with andreciprocating relative to said centrifugal grum, said pusher plateconstituting a second meman inwardly widening acceleration funnelsecured to one of said members for joint rotation therewith,

a conically outwardly widening solid-walled portion secured to one ofsaid members and disposed at a greater radial range relative to therotating axis than the outermost radius of said pusher plate,

a second cylindrical screen portion of a smaller diameter than that ofsaid first cylindrical screen, and having a radius at least equal withthe outermost radius of said pusher plate,

means for feeding said material to be centrifuged toward saidacceleration funnel,

means for feeding washing liquid disposed directly opposite saidsolid-walled portion and feeding washing liquid over substantially theentire area of said solidwalled portion, and

said conically outwardly widening solid-walled portion is secured tosaid pusher plate.

5 6 2. In a pusher type centrifuge with a washing device said secondcylindrical screen portion is secured to said for the centrifugedmaterial: pusher plate at one end and to said solid-walled pora housing,tion at its other end. a centrifugal drum rotatably mounted in saidhousing,

to constitute a first member, 5 References Cited at least one firstcylindrical screen portion extending UNITED STATES PATENTS axially fromsaid centrifugal drum,

a push r-plate disposed Within said housing and rotatguegg ing with andreciprocating relative to said centrifugal 178 7/1958 gg K76) drum, saidpusher plate constituting a second memu e ere ber 10 2,883,054 4/1959Sanchez 210-.377X

an inwardly widening acceleration funnel secured to 2991887 7/1961 Wlrthet 210 376 one of sard members for JOlIlt rotatlon therewith, FOREIGNPATENTS a conically outwardly Widening solid-walled portion secured toone of said members and disposed at a 5 859,429 12/ 1952 Germany.greater radial range relative to the rotating axis than the outermostradius of said pus-her plate, OTHER REFERENCES a second cylindricalscreen portion of a smaller dia- German im d li tion No, 1,030,771, May1958, meter than that of said first cylindrical screen and Germanprinted application No. 1,044,721, November having a radius at leastequal with the outermost 20 1958 radius 0f Said Pusher P German printedapplication No. 1,073,964, January means for feeding said material to becentrifuged 1%() t wa d Said accelfifation funnel, German printedapplication No. 1,079,551, April 1960.

means for feeding washing liquid disposed directly opposite saidsolid-walled portion and feeding Washing 25 REUBEN FRIEDMAN, PrimaryExaminer.

liquid over substantially the entire area of said solid- J L DE CESAREAssistant Examiner walled portion, and 7

